The present invention relates to an apparatus for use when plugging a well within the petroleum industry. More particularly, it relates to an apparatus for use when positioning a fluidized plugging material in an oil well or a gas well which is lined with a casing, the apparatus including: a driving body; a carrier body defined by an indefinite side portion extending between a first end portion and a second, end portion, the carrier body being arranged to be set in motion by the driving body; and at least one displacement member arranged on the carrier body.
When abandoning an oil well or a gas well temporarily or permanently, it is required that the well should be secured with a plugging material which has sufficient strength and tightness to prevent leakage between a petroleum-bearing formation and the surface of the well. To provide such a plug, it is common to fill a portion of the well with a fluidized plugging material. The fluidized plugging material usually comprises a cement slurry for the formation of a hardenable cement plug. But it is to be understood that the fluidized plugging material may comprise a fluidized unconsolidated material for the formation of an unconsolidated-material plug. The description that follows will be directed, to a great extent, towards a cement plug. However, the present invention is also well suited for positioning an unconsolidated-material plug. The extent of the plug in the longitudinal direction of the well is typically 50 meters, but is dependent on international, national or oil/gas contractors' internal requirements.
Till now, it has been common to provide a cement plug by first removing the casing in the area in which the plug is to be established. Such a removal is typically carried out by means of a cutting tool. After the desired portion of the casing has been removed, the wellbore is widened by means of a drilling tool, a so-called “reamer”, to provide a best possible attachment between the plug and the surrounding formation. Then cement is carried into the widened wellbore.
Such a method is very time-consuming and expensive, while, at the same time, metal chips from the casing may result in a need for extensive and expensive maintenance of upstream equipment.
The industry therefore has a strong need for quicker methods, and methods in which the casing is left in the well.
The purpose of the present invention is to provide an apparatus and a method for providing a complete and reliable attachment of a fluidized plugging material in an oil well or a gas well. This is achieved by providing sufficient contact between the surface of the bore to be plugged and the plugging material. The apparatus and the method may be used both when plugging a non-perforated portion of a casing, when plugging a perforated casing, in which the plugging material fills most of the annulus between the formation and the centre of the casing, as well as when plugging a so-called openhole section.
In his Norwegian patent application NO201117641, the present applicant has described a perforation and washing apparatus arranged to prepare a perforated casing for grouting and forming a plug in a well. The plug can be temporary or permanent.
To provide reliable engagement between the casing and the plugging material, and to ensure that an annulus between the outside of the casing and the formation will also be sufficiently plugged by means of the plugging material, there is a need to communicate the plugging material from the inside of the casing to the outside of the casing. But there is also a need to be able to drain away a liquid that might be present in the annulus between the outside of the casing and the formation, so that the liquid will not prevent the inflow of plugging material into said annulus.
From the publication US 2010/039879, an apparatus and a method for agitating a cement slurry in an annulus defined between a formation wall and a casing in a well are known. The apparatus includes a sleeve which is provided with an agitating device and which is arranged to rotate relative to the casing. The apparatus is placed on the outside of a portion of the casing.
From the publication U.S. Pat. No. 4,595,058 a cementing tool for ensuring sufficient sealing of an annulus between a riser and a casing is known. The cementing tool is constituted by a pipe piece which has flow-directing rigid ribs welded thereon to provide a turbulent flow between the riser and the casing when the pipe piece is set in rotation.
From the publication U.S. Pat. No. 4,995,456 an apparatus and a method for providing a gravel pack around a production tubing in a well are known. The apparatus includes helical rigid blades welded on or otherwise attached to a completion tool.